Second layer too far from first

Howdy all. I bought a Prusa i3 kit and have been experimenting with and reading about 3D printing for the past couple weeks and thus far have been able to find answers to all of my questions without asking. Now I've come to a point where I'm at a loss and I must ask for help.

For some reason the second layer of all my prints seems to be slightly too high all of a sudden. I wasn't having this issue until the last couple days. The first layer always looks amazing: thick, gooey, adhered, solid. But then whenever the second layer comes around it looks almost as if the z axis has been raised slightly too high. I don't think it's a problem with flow or temperature because when I manually recalibrate the z-axis during the print everything proceeds beautifully and as normal. The end result when the 2nd layer doesn't cooperate is shown in the attached photo: small spaces in the bottom of the final print. Again, the first and every layer after the second print GREAT... leaving me perplexed.

Also I absolutely cannot seem to get stringing under control without dropping my extrusion temps closer to the bottom of the liquid phase. Around 180 for PLA and I've tried every possible combination of retraction/temperature/speed settings but I always end up with stuff I have to clean up after.

I feel like I'm going insane!

Have you calibrated your Z axis?
Try printing a 20mm cube and see if its 20mm high. If your calibration is off then it should be fairly obvious.

Thanks for the advice. I hadn't. But I just printed a 20x20x10 calibration block and it measures up. Still troubleshooting...

Can anyone tell me how to generate incremental g-code? I know I can change to incremental mode via a single command but I doubt that's very useful without the right numbers populated. I'm thinking if I can switch to incremental I can manually set the second layer slightly lower for the time being and get back to printing. This is becoming very time-consuming!

Right-o well for the time being I'm manually raising the bed a fraction of a millimeter after the first layer with great results. Because science.

Example attached. Closer model printing first. You can see the non-adhesion. And in the further model I've made my Z adjustment, after which the print proceeds as normal. No errors like this between subsequent layers.

Edited 1 time(s). Last edit at 06/24/2016 01:46PM by TwoAndAHalfDimensions.

Quote
TwoAndAHalfDimensions
Example attached. Closer model printing first. You can see the non-adhesion. And in the further model I've made my Z adjustment, after which the print proceeds as normal. No errors like this between subsequent layers.

Looks like the end of the bed closest in the pic may not be as close to the nozzle as the rest. I'd check that your bed is level Also I'd move Z axis down as far as it'll go, measure it's distance to the bed, then move it up as far as it'll go, and measure distance to bed, move it all the way back down, and measure again. Do it a few times, maybe you've got something binding so it's not moving like it needs to on that side.

Thank you for your reply. The model closer to the camera looks that way because I made the adjustment mid-print in order to illustrate the difference. I have calibrated and know that the bed is level.

Also I am doubtful that the binding you've described is the issue. After the second layer every following layer prints as expected with no visible distortion.

Rotating each bed calibration screw a half turn immediately following completion of the first layer 100% solves the issue. Very puzzling.